/*=====================================================================*
 *                   Copyright (C) 2011 Paul Mineiro                   *
 * All rights reserved.                                                *
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 * Redistribution and use in source and binary forms, with             *
 * or without modification, are permitted provided that the            *
 * following conditions are met:                                       *
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 *     above copyright notice, this list of conditions and             *
 *     the following disclaimer.                                       *
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 *     * Redistributions in binary form must reproduce the             *
 *     above copyright notice, this list of conditions and             *
 *     the following disclaimer in the documentation and/or            *
 *     other materials provided with the distribution.                 *
 *                                                                     *
 *     * Neither the name of Paul Mineiro nor the names                *
 *     of other contributors may be used to endorse or promote         *
 *     products derived from this software without specific            *
 *     prior written permission.                                       *
 *                                                                     *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND              *
 * CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,         *
 * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES               *
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE             *
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER               *
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 * Contact: Paul Mineiro <paul@mineiro.com>                            *
 *=====================================================================*/

#ifndef __LOSS_HH_
#define __LOSS_HH_

#include <boost/optional.hpp>
#include <ostream>
#include <string>

namespace flassol
{
  struct Loss
    {
      enum LogLevel
        {
          INFO,
          WARN
        };

      virtual float 
      loss (float p, 
            float y) = 0;

      virtual float 
      dldp (float p, 
            float y) = 0;

      virtual float 
      invariant_update (float p,
                        float wdotx,
                        float adotb,
                        float y,
                        float eta,
                        float anormplusbnorm,
                        float xnorm,
                        float onedotone) = 0;

      virtual std::ostream& 
      report (std::ostream& o,
              LogLevel      level) = 0;
    };

  typedef Loss* (*LossFactory) (const std::string& s);

  LossFactory
  register_loss_factory (const std::string& s,
                         LossFactory        l);

  boost::optional<LossFactory>
  get_loss_factory (const std::string& s);

  std::string
  get_registered_losses ();
}

#endif // __LOSS_HH_
